1. Field of the Invention
The present invention relates to a method and an apparatus for controlling the travel of an automatic guided vehicle to make the automatic guided vehicle travel and stop at intended point.
2. Description of the Prior Art
Various methods have been proposed, and put to practical use, for causing an unmanned vehicle (automatic guided vehicle) to travel from place to place on a plant floor along a route composed of an optical reflective tape or the like, instead of a railed track. One typical known method of the type is illustrated in FIG. 1 by way of example. FIG. 1 is a schematic plan view showing a conventional method of controlling the travel of an automatic guided vehicle. As shown in FIG. 1, a route consists of a line of optical reflective tape R fixed on a floor surface in a loop-form pattern to connect between a start point 0 and a plurality of points A, B . . . in order. A plural of count marks CM, CM . . . composed of a similar reflective tape or the like are separately fixed on the floor at predetermined intervals along the route. An automatic guided vehicle 30, provided with sensors 31 and 32 for detecting reflective tape R as the route and count marks CM, CM . . . respectively, is allowed to run along the route by detecting the reflective tape R by sensor 31. Whilst, the sensor 32 counts the number of count marks CM, CM . . . passed by automatic guided vehicle 30; and each time such counted number reaches the number of count marks CM, CM . . . present over a distance from the start point 0 to each or any of the intended points A, B . . . , the automatic guided vehicle 30 is braked to selectively stop at each or any of the points A, B . . . .
Such control method has a difficulty in that if any obstacles resembling a count mark is present adjacent any point of the route or if any of the count mark CM is stained, some deviation may be caused to the numeric value of counting up to an intended point. Similarly, if an error is made in the counting of count marks CM, CM . . . because of some snaking or the like involved in the travel of the automatic guided vehicle 30 on the way to an intended point, the automatic guided vehicle 30 may stop at a point other than intended point. With errors accumulated, such deviation will naturally become larger as the distance of travel increases. In addition, execution of laying the count-mark requires considerable labor because a large number of count marks are involved.